Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-01-2010, 04:54 PM   #1
Senior Member
piesforyou's Avatar

Join Date: Dec 2009
Photos: Albums
Posts: 129
Strange colours - why did this happen?

My city finally got some snow today (yay) so i went out and started taking some snaps. Anyway the shot below is of a street outside a shop which has blue and red painted shapes on the window glass, and a light behind casting the colours onto the street. However, as you can see some of the blue turned out very odd. They almost look like neon lights. In reality, those areas were just the same as the other bits of colour on the street. Hopefully you can see what I mean.

If it helps, it was shot with a Pentax-M 28mm @ 2.8, ISO 800, 1/10s
White balance was set to "tungsten" modified to M1 B7 (straight to jpeg)



So yeah. What caused that?

12-01-2010, 05:06 PM   #2
Senior Member




Join Date: Jul 2008
Location: Arizona
Posts: 283
Possibly the bright white light across the street just happening to reflect from the area that has the blue? The angle looks about right.

Mike
12-01-2010, 05:18 PM   #3
Senior Member
piesforyou's Avatar

Join Date: Dec 2009
Photos: Albums
Posts: 129
Original Poster
QuoteOriginally posted by Stringmike Quote
Possibly the bright white light across the street just happening to reflect from the area that has the blue? The angle looks about right.

Mike
I don't think it could be because the effect wasn't visible to the eye. It was a suprise when I saw it on my computer. Plus those lights are not very bright at all.
12-01-2010, 05:27 PM   #4
Veteran Member
KxBlaze's Avatar

Join Date: Feb 2010
Location: California
Photos: Gallery
Posts: 1,594
My guess is that even though it was not visible to your naked eye, your camera sensor still could have picked up that reflection. Because beyond that theory I have no idea what could have caused those specific areas to do that while the rest of the photo remains normal.

12-01-2010, 05:55 PM   #5
Veteran Member
Eruditass's Avatar

Join Date: Jul 2009
Location: Pittsburgh, PA
Photos: Gallery | Albums
Posts: 2,206
Narrow bandwidth lighting, such as LEDs, will cause this on RGB bayer sensors, I believe.
12-01-2010, 06:23 PM   #6
Ira
Inactive Account




Join Date: Mar 2009
Location: Coral Springs, FL
Photos: Gallery | Albums
Posts: 5,218
I forget the effects since I last used film, but doesn't tungsten balanced film, and tungsten setting on a DSLR, yield a very blue result when the color temp is actually closer to daylight?
12-01-2010, 06:56 PM   #7
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,043
QuoteOriginally posted by Eruditass Quote
Narrow bandwidth lighting, such as LEDs, will cause this on RGB bayer sensors, I believe.
I suspect we have the correct answer folks.
12-01-2010, 06:58 PM   #8
Ananta Androscoggin
Guest




It looks like the rest of the street is lit by streetlights overhead. They add their own color cast depending on which type of lamps they have, and the ol' Mark I Mod 0 eyeball adjusts quickly enough to it that one often tendss to forget that it isn't really a white light source.

And it looks to me like some parts of the sidewalk have slightly deeper snow than others (more recently swept?), giving patches of different reflectivity off the snow to help complicate the whole light-color question.

Plus it appears that some of the shop's windows aren't colored at all, letting the interior lighting spill outdoors to add their own direct coloring to the scene.

12-02-2010, 03:06 AM   #9
Senior Member
piesforyou's Avatar

Join Date: Dec 2009
Photos: Albums
Posts: 129
Original Poster
I'll check the shop again tonight, take another photo and see if the lights are LED. I'll report back!
12-02-2010, 04:51 PM   #10
Senior Member
piesforyou's Avatar

Join Date: Dec 2009
Photos: Albums
Posts: 129
Original Poster
Unfortunately by the time I got there tonight the lights were switched off, however when I passed earlier on I could see that the lights were Halogen. Now, a quick googling seems to tell me that Halogen lights emit a very large range of wavelengths, from a small amount of UV, peaking in the red and then a large amount of Infra-red. They get hot.

So my guess here would be that the sensor is receiving a lot of UV reflection at those particular points of the blue stripes. It fits, right? The UV would come from the blue rather than the red stripes as the red filters on the window would filter out the UV. Some further brief googling reveals that bayer sensors are indeed sensitive to UV, but that the filters put before the sensor are supposed to filter it out. So.... I guess this is where my physics runs out... If all of the above is true then it means that either a) the UV filters on the bayer sensor are not filtering out 100% of the UV, or that b) the wavelength of the light is not UV when it reaches the sensor. I dunno... over to you guys?
12-02-2010, 04:56 PM   #11
Senior Member
piesforyou's Avatar

Join Date: Dec 2009
Photos: Albums
Posts: 129
Original Poster
Some more googling lends more weight to option a)

Are digital sensors sensitive to UV? - Photography - Stack Exchange

QuoteQuote:
Despite the filtration applied to digital sensors, UV light is still a problem, and can affect color balance.
12-06-2010, 10:04 AM   #12
New Member




Join Date: Dec 2010
Posts: 4
LED do this to sensors; I tried 'painting with light' with LED torches and it didn't work at all! Still i think your picture looks good!
12-06-2010, 01:27 PM   #13
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,817
Snow makes color temperature differences very obvious. There are so many different light sources in that photo, and today you can get so many different light technologies.

You can see the same effect in other common situations. In sunny daylight, snow in the shade will be much bluer than snow in the sun. Using a flash where there's also bright incandescent lights will give you a similar effect.

The funny part is your eyes ignore these massive light differences when you're there, yet when you see the photo later, the same scene accurately recorded looks strange. If you start to look for the color temperature, you'll notice it in the real world too.
12-06-2010, 04:57 PM   #14
Veteran Member
paperbag846's Avatar

Join Date: Jul 2010
Photos: Gallery
Posts: 2,396
This explains the insane colours I get when I take pictures of my flatscreen TV.
08-24-2011, 02:35 AM   #15
Senior Member
piesforyou's Avatar

Join Date: Dec 2009
Photos: Albums
Posts: 129
Original Poster
Apologies for digging up this old thread, but I just looked properly at some photos I took at a wedding reception. This issue is all over them! Take a look.






So these were taken with a K-x, with a M 28mm F2.8. These are direct from RAW with nothing done except resizing.

Now, normally I wouldn't say this is a big issue. But a large proportion of my photos from the reception show this issue, and those that are affected are ruined. It's incredibly unsightly. I think it's halogen lighting again. I suggest the UV filter on the sensor is not cutting out enough of the UV light in this situation. Note that both photos (the original snowy photo and these) are taken in low ambient light conditions where the halogen lighting is prominent. When shooting in these conditions I would strongly suggest using a UV filter on your lens, and look for one which is particularly harsh with cutting out as close to blue as possible. Maybe that will help...
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, colours, pentax help, photography, shot, street
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Colours strange in Firefox Haakan Digital Processing, Software, and Printing 9 07-27-2009 11:31 PM
It had to happen graphicgr8s General Talk 126 03-03-2009 11:02 PM
strange things happen, when ur goen' round the twist! distorted_vision Post Your Photos! 18 11-07-2008 03:59 AM
Why does this happen Fritzvds Photographic Technique 22 08-20-2008 05:32 AM
Now how did that happen? ftpaddict General Talk 11 05-13-2008 12:23 PM



All times are GMT -7. The time now is 09:38 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top